Thermodynamic and quantum chemistry study for dimethylol-5-methyl hydantoin and its derivatives as corrosion inhibitors for carbon steel N-80 in raw water (cooling water system)

Dimethylol-5-methylhydantoin (mhd) was used to synthesis five derivatives that include1,3- di[diethylentriamine)methyl] – 5 -methylhydantoin (dtm); 1,3 -di[ (1,2 -diaminopropyl)methyl ] – 5 –methylhydantoin (dam);1,3-di[oxyethanolamine)methyl]-5-methylhydantoin (dom), and 1,3- di[(1,2-diaminoethyl)methyl]-5-methylhydantoin (dmm), these five compounds have been evaluated as corrosion inhibitors for n-80 carbon steel in raw water (cooling water system). the adsorption of these compounds has been tested thermodynamically which was found to be that the adsorption of them is chemisorption mode on mode. furthermore, some activation thermodynamic parameters such as δh*, δg*, and δ*s of activation have been estimated. in addition, a trial to find a quantitative relationship between the inhibition efficiency and the electronic properties of the inhibitor molecules was carried out. on the other hand, inhibitor mhd has higher efficiency than other inhibitors because the ehomo, elumo-ehomo, has higher values in presence of mhd than other inhibitors, and has positive δg value, while in case of other inhibitors are negative values, and the partial charge on hetero atoms δ in case of inhibitor mhd negative while in others are positive values